Soapy water is good for your roses
Never plant a new rose in the spot where you have dug up an old rose, as it may not thrive, says Good Housekeeping. You must mulch your rose beds in the summer after rain.
To keep your roses free from black spots, rake up and kill fallen leaves. They cause the black spot. Remember to plant roses deep enough for the budding point above the roots to be slightly below the surface.
A 0.5 per cent solution of baking soda (bicarbonate of soda) and water (3 teaspoons baking soda per gallon of water) sprayed on roses is a good medicine to treat black spot and powdery mildew. (Based on research by R.K. Horst, professor of plant pathology at Cornell University.
Try this safe soap spray: One teaspoon Shaklee’s Basic H per gallon of water, or 1 tablespoon Ivory liquid per gallon of water. Soap sprays are sturdy killers of soft-bodied insects like aphids, scale and white flies!
You can use a one and a half to 2 per cent solution for most liquid household soaps. From Slug Bread & Beheaded Thistles by Ellen Sandbeck.